ATLANTA — The city comes as a lovely surprise: warm, lush, green, wooded and--clean. No graffiti here, or almost none. Amazing.

You can get around Atlanta on a friendly convenience called MARTA (Metropolitan Atlanta Rapid Transit Authority). Or, of course, you can drive. Traffic is heating up around here, but even rush hour remains manageable. Atlanta's Buckhead area in the city's heart has a spectacular array of well-kept lawns, tall trees and stately mansions. If it isn't always the Old South we're looking at, the New Affluence has retained a seductive veneer of Southern grace.

And Southern theater? . . . It is partly haunted by the same veneer and partly working to break free of it. Those who practice theater in this Southeastern corridor say they feel good about it.

They said it at a seminar called "Southern Voices . . . Who's Listening?" held in conjunction with the annual meeting of the American Theatre Critics Assn. in this city late last month.

They talked about an upswing in the arts, and about the sheltered freedom here to try and fail, living being cheap and state and county arts support generous.

But they also talked about de facto segregation (in the city and their audiences if not in their theaters), about the absence of black critics on white papers and about regionalism as a resistance movement to fight homogenization of the culture.

"If you're a sculptor from this area," said panelist/playwright Jim Grimsley, "you may create something that will be appreciated all over the world, but the clay will be from here."

Yet behind the candor, one sensed a degree of wishful thinking. And what could be seen on Atlanta's stages in the five days that the critics' meeting lasted reinforced this perception.

Audiences are lean and hard to get for anything but the Academy and the Alliance Theaters. These remain the undisputed flagships.

Frank Wittow, founder and artistic director of the Academy since 1956, had a stylish production of Craig Lucas' "Three Postcards" (which premiered at South Coast Rep in Costa Mesa in 1987) on one stage and Roberto Athayde's stinging political parable, "Miss Margarida's Way," on the other. The Academy is finding its 1988-89 season to be its best ever, with sales expected to top 31,500 tickets--or a 24% improvement over last year.

At the Alliance, which claims to be playing to 93% capacity and to derive 60% of its income from earnings, "Amadeus" and "Driving Miss Daisy" were the attractions. Indeed, Miss Daisy is an Atlanta dowager and playwright Alfred Uhry is a native.

With the possible exception of "Three Postcards," these are safe mainstream choices, reflecting the criticism most often leveled at Atlanta's audiences by its theater critics: That of a "lingering conservatism" favoring shows that don't rock the boat. A day-trip across state lines to the Alabama Shakespeare Festival suggested that this preference for passivity extends beyond city limits.

The 17-year-old Shakespeare festival, which started in Anniston, moved five years ago into a state of the art $21.5 million two-theater complex outside Montgomery. It's an idyllic setting, amid the greenest fields and shimmering ponds. Yet at what might be viewed as a crowning moment in this theater's evolution, founding artistic director Martin Platt is leaving.

"It's partly the 17 years," he said diplomatically, "partly a desire to move to a more culturally driven community." On view was his final show: a traditional but striking "Cyrano de Bergerac," with a gifted Greg Thornton in the title role. A classy farewell to arms. Platt, a native of Beverly Hills, leaves July 16--the end of the season--for points North and East. Meanwhile, the search is on for a replacement. Unofficially, the word is that the board wants someone who'll provide "audience-friendly" Shakespeare.

And so it goes. Is it that Southern audiences have avoided exciting new theater or that the new theater has failed them by not being exciting enough? It's an old chicken-egg question, but the truth is that most of what passed for new or experimental on the Atlanta boards the week of the critics' meeting was remarkably unprepossessing.

Take Richard J. Allen's "The Man Who Killed Rock Monenoff" at Theatre in the Square (in the Atlanta suburb of Marietta). It follows the permutations of a dim and corpulent young man who accidentally runs over a rock star and kills him. This new play by the associate head writer for NBC's "Days of Our Lives" aims at satirizing trash TV, yet resorts to sitcom tactics to get the job done--down to a woman born to shop and a cloyingly kooky love interest. At intermission a portion of the audience defected to a city-sponsored jazz concert on the square. Not good manners, but an option on a warm night.